Two-stage linear peristaltic pump mechanism

ABSTRACT

This invention discloses a peristaltic pump composed of a two-stage linear peristaltic pump mechanism, which engages in different functions, charging and pumping a fluid to a patient. This peristaltic pump is capable of restoring the crushed tubing, caused by repeated compression or crushing of the tubing by peristaltic fingers, to its original circular cross sectional area so that it can provide a precise flow rate. The two-stage linear peristaltic pump mechanism substantially improves the consistency of a flow rate over time and extends the usefulness of peristaltic pumps to applications where they could not otherwise be used.

BACKGROUND OF THE INVENTION

This invention is related to a peristaltic pump that is capable ofproviding a precise and substantially consistent flow rate over asubstantial cumulative operating time including by maintaining orrestoring crushed or deformed tubing back to its original circular crosssection.

When linear peristaltic mechanisms are used as the fluid pumping devicein standard tubing large volume infusion pumps, a problem in maintainingflow rate accuracy is inherent over time due to a tubing crush. Thetubing crush is caused by repeated compression or crushing of the tubingby the peristaltic fingers. The crush can create a set that does notallow the tubing over time to return to its original circular crosssection, but rather it becomes more and more elliptical. Since the crosssectional area of an ellipse is less than the original circle, the flowrate diminishes over time as the cross sectional area diminishes.

Some pumps use silicone or Silastic tubing which is more resilient andtherefore less likely over time to suffer a diminishment in crosssectional area. However, Silastic tubing is more expensive than standardtubing as well as being proprietary in nature and not being availablefrom multiple sources.

In other pumps compensation for the reduction in the flow rate isprovided by running the motor faster over time. A predictive algorithm,typically in software, is used to determine how fast to run the motorover time. However, software algorithms to compensate are approximationsat best and subject to significant error because of inevitablevariations in tubing durometer that occur from production lot to lot.

Some ways to control flow rate in pumps are disclosed in U.S. Pat. No.5,431,634, U.S. Pat. No. 7,559,926, and U.S. Pat. No. 7,566,209. U.S.Pat. No. 5,431,634 used a diaphragm pump to maintain an output volumesubstantially constant notwithstanding substantial variation in fluidpressure from a fluid supply or variation in ambient pressure. U.S. Pat.No. 7,559,926 details an implantable infusion drug pump that pumps afluid into a main reservoir then out through a flow restrictor. Therestrictor is able to limit the flow rate to the extent dictated by amotivating force, fluid viscosity, and restriction. U.S. Pat. No.7,566,209 relates to a peristaltic pump that controls the volume of thefluid in the tubing utilizing a magnetic and/or an electric field.However, none of those patents provides a mechanism capable ofaccurately compensating for the reduction of the flow rate due to thetubing crushing inherent in a peristaltic pump by restoring the crushedtubing to its original circular cross section.

SUMMARY

A peristaltic pump having a tubing in a fluid communication with areservoir containing a fluid, the peristaltic pump comprises a two-stagelinear peristaltic pump mechanism: one stage linear peristaltic pumpmechanism ensures a crushed area of the tubing on which the other stagepump mechanism operate to return to its original cross sectional areaand to provide a consistent flow rate of the fluid. These and otherfeatures, aspects, and advantages of the present invention will becomebetter understood with reference to the following description, appendedclaims, and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of the peristaltic pump assembly accordingto an exemplary embodiment of the present invention;

FIG. 1B is a partial sectional view of FIG. 1A;

FIG. 2A is an isolated perspective view of operation of the chargingmechanism, sub-assembly of the peristaltic pump of FIG. 1A;

FIG. 2B shows a charging cycle for the charging mechanism of FIG. 2A;

FIG, 2C is similar to FIG, 2A but is a view of the pumping mechanism ofthe peristaltic pump;

FIG. 2D shows a pumping cycle for the pumping mechanism of FIG. 2C;

FIG. 3 is an exploded view of the peristaltic pump subassembly;

FIG. 4 is an enlarged view of a charging occluder mechanism according toan exemplary embodiment of the present invention;

FIG. 5 is a block diagram of one exemplary electronics control;

FIG. 6 shows a flowchart of the program to operate the peristaltic pumpof this invention,

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention provides that a crushed area of a piece of tubingcaused by repeated press of a peristaltic pump 8 is always returned toor toward its original cross sectional area with each pump cycle. Thus,this provides an equal or a substantially equal flow rate of a fluid ineach cycle deterring or eliminating a flow reduction problem. In oneaspect of the invention, this return to substantially original crosssectional area for the tubing is accomplished by using a two-stageslinear peristaltic pump mechanism 12. Specifically, one stage linearperistaltic pump mechanism ensures a crushed area of the tubing on whichthe other stage pump mechanism operate to return to its original crosssectional area and to provide a consistent flow rate of the fluid.

The two-stage linear peristaltic pump mechanism 12 can be used for anypumping function including but not limited to providing a fluid to aspray nozzle as but one example. Another example is an infusion pump.Because the two-stage linear peristaltic pump mechanism 12 substantiallyimproves flow rate consistency over time, the two-stage linearperistaltic pump mechanism 12 extends the usefulness of peristalticpumps to applications where they could not otherwise be used.

Referring to FIGS. 1A and 1B, there is shown three dimensional andfront, partial views of one embodiment of the assembly of theperistaltic pump 8 made in accordance with the present invention. Apiece of tubing 16 in fluid communication with a reservoir 10 containinga fluid is used together with the peristaltic pump 8. The two-stagelinear peristaltic pump mechanism 12 comprises two separatelycontrolled, but cooperatively working, pumping stages. They are anupstream linear peristaltic charging mechanism 22 (charging mechanism22) and a downstream linear peristaltic pumping mechanism 24 (pumpingmechanism 24). The charging mechanism 22 and the pumping mechanism 24are successively along the upstream portion of the tubing 16 a, acharging section 18 of the tubing 16, and downstream portion of thetubing 16, a pumping section 20 of the tubing 16, to infuse a fluid to apatient through the tubing 16. The charging mechanism 22, acting uponthe charging section 18 of the tubing 16, pumps the fluid from thecharging section 18 of the tubing 16 into the pumping section 20 of thetubing 16. The charging mechanism 22 is responsible for ensuring thatthe pumping section 20 of the tubing 16, which will subsequently beacted on by a pumping mechanism 24, is fully extended or is filled to anextent as specified and under pressure, countering the effects of anycrushing it may have experienced, before the pumping mechanism 24 beginsits work. The pumping mechanism 24, acting upon the pumping section 20of the tubing 16, pumps the fluid from the pumping section 20 of thetubing 16 into a patient at an equal or a substantially equal flow rate.

The tubing 16 is any of a number of standard commercially availableintravenous tubing with different inner diameters.

The charging mechanism 22 comprises a plurality of peristaltic chargingfingers 30 a and a charging shaft 26 a; the pumping mechanism 24comprises a plurality of peristaltic pumping fingers 30 b and a pumpingshaft 26 b. In one embodiment, the charging shaft 26 a and pumping shaft26 b are crank shafts; in another embodiment, cam shafts are used inreplacement of those crank shafts. The number of peristaltic chargingfingers 30 a and peristaltic pumping fingers 30 b are 5-14 or 5-8.

A motor or two motors 34 such as DC motor, step motor, or brush motor orbrushless motor, not limited to the aforementioned, drives a motor shaft40 that turns the charging shaft 26 a and the pumping shaft 26 b in asuccessive series. In one embodiment, each shaft of the charging shaft26 a and the pumping shaft 26 b is independently driven by a same singlemotor 34 in one direction via one-way clutches 44 a and 44 b such assprag or roller clutches, which allow a motor to drive in one directionbut to disengage in the other direction.

In one embodiment, the motor 34 is a single DC gear motor. The motor 34together with a quadrature encoder 36 and those two roller clutches 44 aand 44 b drives, via the motor shaft 40 connected with the motor 34 and,through a motor gear 42, via a main shaft 48, the charging mechanism 22and the pumping mechanism 24 in series. Main gears 46, 46 a, and 46 bare attached on or connected with the main shaft 48. The main gear 46drives either the main gear 46 a or 46 b in one direction and disengagein the other direction while 46 a and 46 b separately runs gears 32 a,which is in connection with the charging shaft 26 a, and 32 b, whichruns the pumping shaft 26 b. The motor 34 can be any of a number ofcommercially available motors such as the Maxon Amax series, Maxon MotorInc., Fall River, Mass. including an integral quadrature encoder 36,detecting the speed and direction of the motor 34, and a gear box 38,slowing down the speed of the motor 34 and at the same time increasingpower output. The motor 34 is attached to a base 50 or an equivalentstructure for steadfastness.

In one embodiment, the motor 34 is a single DC gear motor together witha quadrature encoder 36 and the two roller clutches 44 a and 44 bdriving, via the motor shaft 40 connected with the motor 34, thecharging mechanism 22 and the pumping mechanism 24 in series. The maingears 46, 46 a, and 46 b are attached on or connected with the motorshaft 40. The main gear 46 drives, either the main gear 46 a or 46 b, inone direction and disengage in the other direction while main gears 46 aand 46 b separately run the gear 32 a, which is in connection with thecharging shaft 26 a, and the gear 32 b, which is in connection with thepumping shaft 26 b.

The quadrature encoder 36 is used to control the speed and direction ofthe motor 34. When the motor 34 turns in one direction, one of those twoone-way clutches 44 a mating the main gear 46 a and 44 b mating the maingear 46 b via either the gear 32 a or 32 b, or directly engages turningone of two shafts, the charging shaft 26 a and the pumping shaft 26 b.

Referring to FIGS. 2A, 2B, 2C, and 2D, the charging mechanism 22 isdesigned so that, when the motor 34 is driving in the clockwisedirection, the charging mechanism 22 is driven by the roller clutch 44 aand the peristaltic charging fingers 30 a produce a downstreamperistaltic wave. The pumping mechanism 24 is designed so that, when themotor 34 is running in the counterclockwise direction, the pumpingmechanism 24 is driven by the roller clutch 44 b and the plurality ofperistaltic pumping fingers 30 b produce a downstream peristaltic wave.Thus, the running direction of the motor 34 controls which mechanism isproviding the downstream peristaltic wave, and each of the chargingmechanism 22 and the pumping mechanism 24 operates independent of theother; in other words the speed and rotation direction of each mechanismis separately controlled, but those two mechanism work cooperatively.

The plurality of peristaltic charging fingers 30 a, sized around thecharging shaft 26 a, and the plurality of peristaltic pumping fingers 30b, sized around the pumping shaft 26 b, when the charging shaft 26 a andthe pumping shaft 26 b are turning, either compress the tubing 16against a surface of a back member 74 or release the tubing 16.

In one embodiment, the peristaltic pump 8 further comprises a chargingoccluder mechanism 62 a positioned at the downstream of the chargingsection 18 of the tubing 16 and a pumping occluder mechanism 62 bpositioned at the downstream of the pumping section 20 of the tubing 16.In one embodiment, the charging occluder mechanism 62 a comprises atleast one finger of the plurality of peristaltic charging fingers 30 aadjacent to the pumping section 20 of the tubing 16. The chargingoccluder mechanism 62 a is able to compress the tubing 16 shut againstthe backing member 74 and to prevent backflow, when the pumpingmechanism 24 is in operation. The pumping occluder mechanism 62 bcomprises at least one selected from the group consisting of at leastone finger of the plurality of pumping fingers 30 b and/or an occluderfinger 58, at the downstream of the pumping section 20 of the tubing 16.The pumping occluder mechanism 62 b is able to press the tubing 16 shutagainst the backing member 74 for the prevention of leakage, when thecharging mechanism 22 is in operation.

Referring to FIGS. 2A, 2B, 2C, and 2D, in operation, pumping the fluidto the patient is accomplished by the action of the charging mechanism22 and the pumping mechanism 24 in successive sequence. Referring toFIGS. 2A and 2B, at the conclusion of one peristaltic cycle, the pumpingoccluder mechanism 62 b presses the tubing 16 shut against the backingmember 74 to prevent leakage, and then, the motor 34 turns in aclockwise direction so that the charging mechanism 22 pushes the fluidfrom the charging section 18 of the tubing 16 toward the pumping section20 of the tubing 16, eventually filling the pumping section 20 of thetubing 16 with the fluid. The motor 34 continues to turn and the fillingof the pumping section 20 of the tubing 16 continues until a transducer54 indicates that the pressure in the pumping section 20 of the tubing16 has reached a level that the pumping section 20 of the tubing 16 hasbeen fully filled with the fluid and is fully extended to restoredeformed pumping section 20 of the tubing 16 to original orsubstantially original cross sectional area, or has been filled to anextent as specified. Then, referring to FIGS. 2C and 2D, the motor 34stops turning clockwise and starts driving in a counterclockwisedirection. The charging mechanism 22 now doesn't turn, thus remains inits final position and the charging occluder mechanism 62 a compressesthe tubing 16 shut against the backing member 74 to prevent backflow.The pumping mechanism 24 is operating on the now filled pumping section20 of the tubing 16 and pumps the fluid that was filling the pumpsection 20 of the tubing 16 toward the patient.

The transducer 54 is positioned in contact with an outer wall of thetubing 16 just on or beyond the pumping section 20 of the tubing 16 tomeasure a pressure of the outer wall of the pumping section 20 of thetubing 16. One embodiment of the transducer 54 is a force sensingresister. Another embodiment of the transducer 54 is a piezoelectricsensor.

In one embodiment, the peristaltic pump 8 is designed such that thecharging mechanism 22 fills the pumping section 20 of the tubing 16 inabout 30 seconds or less or a duration prescribed by an administrationof a medication to have more continuous flow. To realize such a quickfilling, in one embodiment, the pumping section 20 of the tubing 16 issufficient short, and/or the motor 34 turns the charging shaft 26 asufficient fast, and/or a total surface of the plurality of peristalticcharging finger 30 a, which is in contact with the charging section 18of the tubing 16, is larger than that of the plurality of peristalticpumping finger 30 b.

Referring to FIG. 3, each shaft, the charging shaft 26 a and the pumpingshaft 26 b, supported by end caps 52 a, b and c and attached to asupport element such as a pump train mount 56 or an equivalent for thepurpose of steadfastness.

Holding elements such as clamps 68 a and 68 b or their equivalents holdthe tubing 16 in place. In one embodiment, the peristaltic pump 8 has abuffer mechanism 71 limiting potential damage forces and providingadjustment compliance when the occluder finger 58 compresses the tubing16 shut. One embodiment of the buffer mechanism 71 comprises an occluderbacker 72 together with a springs 78 held in a spring cap 76 by a setscrew 80. The occluder backer 72, which is retained in position by afoot retainer 70, is made of a resilient material such as plastics. Theoccluder backer 72 and the spring 78 are positioned over the occluderfinger 58.

In one embodiment, referring to FIG. 4, a pin 60 connected with a biaselement 64, a spring or an equivalent, is affixed on the occluder finger58, which is sized around the pumping shaft 26 b and is run by thepumping shaft 26 b. The bias element 64 is further connected with a pin66 affixed on the pump train mount 56. Referring to FIGS. 2A, 2B, 2C,and 2D, during the time the charging mechanism 22 is operating, theoccluder finger 58 compresses close the downstream of the pumpingsection 20 of the tubing 16; during the time the pumping mechanism 24 isoperating and is moving the fluid to the patient, the spring 64rhythmically pulls the occluder finger 58 away from the downstream ofthe pumping section 20 of the tubing 16 with the rotation of the pumpingshaft 26 b.

FIG. 5 shows one example of an electronics control for operating theperistaltic pump 8. An electronics circuit board 90 comprises a mainprocessor 86 and a motor processor 84. Rotary positions 82 of thecharging mechanism 22 and the pumping mechanism 24 relative to therotary position of the motor shaft 40 are prestored in the motorprocessor 84. The transducer 54 measuring the pressure of the outer wallof the pumping section 20 of the tubing 16 feeds pressure data to themotor processor 84; the motor processor 84 monitors the speed anddirection of the motor 34 by the encoder 36. At that point when thetransducer 54 indicates that the pumping section 20 of the tubing 16 hasbeen fully filled with the fluid or has been filled to an extent asspecified, the motor 34 controlled by the encoder 36 stops turningclockwise and starts driving in a counterclockwise direction aftertaking into consideration the rotary positions 82. In contrast, at thepoint when the pumping section 20 of the tubing 16 is empty orsubstantially empty, the motor 34 controlled by the encoder 36 stopsturning counterclockwise and starts driving in a clockwise directionafter taking into consideration the rotary positions 82. In oneembodiment, the emptiness and substantial emptiness is indicated by thetransducer 54. Alarm 88 is connected to the main processor 86 and thealarm 88 is activated by the main processor 86 to warn when anyspecified operative faults occur. A display 92, keypad 94, and electricpower 96 are connected to the main processor 86.

In one embodiment, the two-stage linear peristaltic pump mechanism 12further comprises a two-stage pumping mechanism program which operatesthe peristaltic pump 8; FIG. 6 illustrates how the two-stage pumpingmechanism program operates the peristaltic pump 8. In Step 100, to startthe operation of the peristaltic pump 8, the motor 34 runs to drive thepumping mechanism 24 so that a pumping occluder mechanism 62 b closesthe downstream of the pumping section 20 of the tubing 16. In Step 102,the motor 34 runs to drive the charging mechanism 22 and fill thepumping section 20 of the tubing 16 while the motor 34 disengages thepumping mechanism 24. In Step 104, a determination is made as to whetherthe transducer 54′s pressure is greater than or equal to a predeterminedvalue indicating that the pumping section 20 of the tubing 16 has beenfilly extended or it has been filled to an extent as specified. If “no”in Step 104, go to Step 102; if “yes,” go to Step 106. In Step 106, themotor 34 continues running to drive the charging mechanism 22 so thatthe charging occluder mechanism 62 a presses the charging section 18 ofthe tubing 16 shut to prevent backflow. In Step 108, the motor 34 runsto drive the pumping mechanism 24 and to move the fluid further alongwhile the motor 34 disengages the charging mechanism 22. In Step 114, adetermination is made as to whether the pumping mechanism 24 hasfinished a requested pumping task. If “yes,” go to Step 100; if “no,” goto Step 108. In Step 110, an inquire is made as to whether thetransducer 54 is measuring a pressure greater than or equal to apredetermined threshold occlusion value such as 15 psi indicating thatan occlusion may exist If “yes” is an answer to this inquiry, the alarm88 warns and the motor 34 stops. In one embodiment, the requestedpumping task is defined to empty or substantially empty the pumpingsection 20 of the tubing 16.

The above examples are illustrative only. Variations obvious to thoseskilled in the art are a part of the invention. Additionally, thepresent invention does not require that all of the advantageous featuresand all of the advantages stated need be incorporated into everyembodiment.

1. A peristaltic pump having a piece of tubing in a fluid communicationwith a reservoir containing a fluid, the peristaltic pump comprising atwo-stages linear peristaltic pump mechanisms, wherein one stage linearperistaltic pump mechanism ensures a crushed area of the tubing on whichthe other stage pump mechanism operate to return to its original crosssectional area and to provide a consistent flow rate of the fluid.
 2. Aperistaltic pump as recited in the claim 1, wherein the two-stageslinear peristaltic pump mechanism comprising a charging mechanism alongthe upstream portion of the tubing—a charging section of the tubing anda pumping mechanism along the downstream portion of the tubing—a pumpingsection of the tubing, wherein when a pumping mechanism is notoperating, the charging mechanism operates on the charging section ofthe tubing to fill the pumping section of the tubing with the fluid,wherein when said charging mechanism is not operating, the pumpingmechanism operates on the pumping section of the tubing to moves saidfluid further along.
 3. A peristaltic pump as recited in claim 2,wherein the charging mechanism comprising a charging shaft and aplurality of peristaltic charging fingers sized around the chargingshaft, wherein the pumping mechanism comprising a pumping shaft and aplurality of peristaltic pumping fingers sized around the pumping shaft.4. A peristaltic pump as recited in claim 3, further comprising abacking member, wherein when the charging mechanism is operating, thecharging shaft turns the plurality of peristaltic charging fingers tocompress the charging section of the tubing against the backing member,wherein when the pumping mechanism is operating, the pumping shaft turnsthe plurality of peristaltic pumping fingers to compress the pumpingsection of the tubing against the backing member.
 5. A peristaltic pumpas recited in claim 4, wherein further comprising a charging occludermechanism positioned at the downstream of the charging section of thetubing.
 6. A peristaltic pump as recited in claim 5, wherein thecharging occluder mechanism comprising at least one finger of theplurality of peristaltic charging fingers at the downstream of thecharging section of the tubing.
 7. A peristaltic pump as recited inclaim 4, wherein further comprising a pumping occluder mechanismpositioned at the downstream of the pumping section of the tubing.
 8. Aperistaltic pump as recited in claim 7, wherein the pumping occludermechanism comprising at least one selected from the group consisting ofat least one finger of the plurality of pumping fingers, an occluderfinger at the downstream of the pumping section of the tubing, or anycombination thereof.
 9. A peristaltic pump as recited in claim 8,wherein the occluder finger, fitting around the pumping shaft, isconnected with a bias element with an end fixed onto the peristalticpump, wherein the occluder finger is pulled away from the tubing by thebias element when the pumping mechanism is in operation.
 10. Aperistaltic pump as recited in claim 3, wherein the pumping shaft is acrank shaft or a cam shaft, wherein the charging shaft is a crank shaftor a cam shaft.
 11. A peristaltic pump as recited in claim 2, furthercomprising at least one driver, wherein said at least one drivers isconnected to turn at least one from the group consisting of saidcharging mechanism and said pumping mechanism.
 12. A peristaltic pump asrecited in claim 11, wherein the at least one driver is at least onemotor.
 13. A peristaltic pump as recited in claim 12, wherein a singlemotor is connected to turn both the charging mechanism and the pumpingmechanism.
 14. A peristaltic pump as recited in claim 13, furthercomprising at least two clutches, wherein the at least two clutchesconnected to so said motor turn said charging mechanism to operate onsaid charging section of the tubing when said motor rotates in a firstdirection while disengaging said pumping mechanism, and turn saidpumping mechanism to operate on said pumping section of the tubing whensaid motor rotates in a second direction while disengaging said chargingmechanism, wherein said second direction is opposite said firstdirection.
 15. A peristaltic pump as recited in claim 14, wherein saidat least two clutches are roller clutches.
 16. A peristaltic pump asrecited in claim 15, further comprising a first roller clutch and asecond roller clutch, wherein said first roller clutch is connected forturning said charging mechanism, wherein said second roller clutch isconnected for turning said pumping mechanism.
 17. A peristaltic pump asrecited in claim 16, comprising at least one first gear coupled with thefirst roller clutch in connection to and turning said chargingmechanism, and at least one second gear coupled with the second rollerclutch in connection to and turning said pumping mechanism.
 18. Aperistaltic pump as recited in claim 2, wherein the charging mechanismand the pumping mechanism are operated in a successive series.
 19. Aperistaltic pump as recited in claim 14, further comprising an encodercontrolling the turning speed and direction of the motor.
 20. Aperistaltic pump as recited in claim 19, further comprising a transducerpositioned in the contact with an outer wall of the pumping section ofthe tubing, wherein when the transducer indicates the pumping section ofthe tubing has been fully filled and is fully extended, or has beenfilled to an extent as specified with the fluid, the charging mechanismceases operation and the pumping mechanism starts running.
 21. Aperistaltic pump as recited in claim 20, wherein the transducer is aforce sensing resister or a piezo electric sensor.
 22. A peristalticpump as recited in claim 3, further comprising a rapid chargingmechanism.
 23. A peristaltic pump as recited in claim 22, wherein therapid charging mechanism comprising at least one selected from the groupconsisting of a sufficient short pumping shaft, sufficient fast turningrate of the charging shaft, a total surface of the plurality ofperistaltic charging fingers is, which are in the contact with thecharging section of the tubing, larger than that of the plurality ofperistaltic pumping fingers, or any combination thereof.
 24. Aperistaltic pump as recited in claim 7, further comprising a buffermechanism positioned over the pumping occluder mechanism to prevent thepumping occluder mechanism from doing damages to the tubing and toprovide compliance adjustment.
 25. A peristaltic pump as recited inclaim 24, wherein the buffer mechanism comprising at least one selectedfrom the group consisting of an occluder backer, a spring held in placeby a holding member, or any combination thereof, wherein the occluderbacker is made of a resilient material.
 26. A peristaltic pump asrecited in claim 20, wherein two-stage linear peristaltic pump mechanismfurther comprising a motor processor to operate the peristaltic pump,wherein rotary positions of the charging mechanism and the pumpingmechanism relative to the rotary positions of the motor shaft areprestored in the motor processor, wherein the transducer and the encoderare operatively connected with the motor processor to control theturning speed and direction of the motor.
 27. A peristaltic pump havinga piece of tubing in a fluid communication with a reservoir containing afluid, and a two-stage linear peristaltic pump mechanism—a chargingmechanism and a pumping mechanism—to ensure a crushed area of the tubingto return to its original cross sectional area, the peristaltic pumpcomprising a two-stage pumping mechanism program to operate thetwo-stage linear peristaltic pump mechanism.
 28. A peristaltic pump asrecited in claim 27, wherein the two-stage pumping mechanism programdirects the charging mechanism and the pumping mechanism to act insuccessive series.
 29. A peristaltic pump as recited in claim 28, (a)wherein the two-stage pumping mechanism program directs the chargingmechanism to operate on the upstream portion of the tubing—a chargingsection of the tubing, after directing a pumping occluder mechanism toclose the downstream portion of the tubing—a pumping section of thetubing, to fill the pumping section of the tubing; (b) wherein when atransducer positioned in the contact with the outer wall of the pumpingsection of the tubing indicates that the pumping section of the tubinghas been fully extended or has been filled to an extent as specified,the two-stage pumping mechanism program directs the pumping mechanism tooperate on the pumping section of the tubing after directing a chargingoccluder mechanism to close the downstream of the charging section ofthe tubing to move the fluid further along; and (c) wherein when thepumping mechanism finishes a requested pumping task indicated by thetransducer, the two-stage pumping mechanism program directs the pumpingoccluder mechanism to close up the downstream of the pumping section ofthe tubing and then start the operation of the charging mechanism, andanother pumping cycle starts.
 30. A peristaltic pump as recited in claim29, wherein when the transducer detects a pressure greater than anocclusion value, the two-stage pumping mechanism program instructs theperistaltic pump to stop running.
 31. A method of ensuring a crushedarea of a piece of tubing in a fluid communication with reservoircontaining a fluid, on which a peristaltic pump presses, to return toits original cross sectional area and to provide equal volume of thefluid in each pumping cycle comprising (a) providing the peristalticpump comprising two separately controlled pumping stages, a chargingmechanism and a pumping mechanism, successively along the upstreamportion of the tubing—a charging section of the tubing and thedownstream portion of the tubing—a pumping section of the tubing; (b)operating the charging mechanism on the charging section of the tubingto fill the pumping section of the tubing with the fluid when thepumping mechanism is not operating; and (c) operating the pumpingmechanism on the pumping section of the tubing to move the fluid furtheralong when the charging mechanism is not operating.
 32. The method asrecited in claim 31, further comprising providing at least one motor,wherein the at least one motor is connected to turn at least one fromthe group consisting of the charging mechanism and the pumpingmechanism.
 33. The method as recited in claim 32, wherein a single motoris connected to turn both the charging mechanism and the pumpingmechanism.
 34. The method as recited in claim 33, further comprisingproviding at least two clutches wherein said at least two clutchesconnected to so said motor turns said charging mechanism to operate onthe charging section of the tubing when the motor rotates in a firstdirection while disengaging said pumping mechanism, and wherein saidmotor turns said pumping mechanism to operate on said pumping section ofthe tubing when said motor rotates in a second direction whiledisengaging said charging mechanism, wherein said second direction isopposite said first direction.
 35. The method as recited in claim 34,further comprising providing a transducer positioned in the contact withthe outer wall of the tubing beyond the pumping section of the tubing,wherein when the transducer indicates the pumping section of the tubinghas been fully filled with the fluid and has been fully extended or hasbeen filled to an extent as specified, the charging mechanism ceasesoperation and the pumping mechanism starts running.